The present invention relates to a hydraulic apparatus providing a base, pumps fitted into and secured to the base, the pumps each having annular discharge passages formed between the pumps and the base, damper chambers each connected to the discharge passages, and a hydraulic equipment connected via orifices to the discharge passages.
Further, the present invention relates to an anti-lock brake control apparatus for a vehicle, in which the apparatus has a base arranging normally open electromagnetic valves for connecting and breaking the communication between a master cylinder and wheel brakes, normally closed electromagnetic valves for connecting and breaking the communication between reservoirs and the wheel brakes, return pumps with suction vents connected to the respective reservoirs, dampers each connected to discharge vents of the return pumps, and orifices each interposed between the return pumps or the dampers and the normally open electromagnetic valves. The base further arranges connecting holes serving as threaded holes each coaxial with the orifices, a sheet pipe secured so that it is located at the inner ends of the connecting holes, conduits connected to the master cylinder, the conduit having a flare portion adhering to the sheet pipe at an end of the conduit, and a screw member fitted to the outer periphery of the conduit and screwed into the connecting hole by pressing the flare portion against the sheet pipe.
Conventionally, a hydraulic apparatus and an anti-lock brake control apparatus of such a type as introduced above have been proposed in Unexamined Japanese Utility Model Publication No. Hei. 3-13268.
With the conventional hydraulic apparatus, the damper chamber communicates with the first discharge vent formed on the downstream side of the annular discharge passage, and the orifice communicates with the second discharge vent formed on the upstream side thereof so as to prevent air from accumulating in the annular discharge passage. Despite the provision of the damper chamber and the orifice to prevent the discharge pulsation from the pump from affecting the hydraulic equipment in trouble, the damper chamber and the orifice exhibit an inherent damping action of themselves but they are hardly capable of effectively exhibiting a damping action as a whole of the hydraulic apparatus because the annular discharge passage has great flow resistance and is interposed between the damper chamber and the orifice.
With the conventional anti-lock brake control apparatus, moreover, the sheet pipe and the orifices employed as separate members have been forced into and secured with a clearance provided therebetween in the axial direction. For this reason, the number of component parts tends to increase, and the dust produced at the time when the sheet pipe is forced into the base not only cause the orifices to be clogged but also cause the normally open electromagnetic valves to malfunction when the dust flow into the valve. If, moreover, the orifices are forced into and fixed thereto unsatisfactorily, the orifices slip out because of the discharge pressure in the return pumps.